bootstrap-scrollspy.js

/* =============================================================
 * bootstrap-scrollspy.js v2.0.2
 * http://twitter.github.com/bootstrap/javascript.html#scrollspy
 * =============================================================
 * Copyright 2012 Twitter, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ============================================================== */

!function ( $ ) {

  "use strict"

  /* SCROLLSPY CLASS DEFINITION
   * ========================== */

  function ScrollSpy( element, options) {
    var process = $.proxy(this.process, this)
      , $element = $(element).is('body') ? $(window) : $(element)
      , href
    this.options = $.extend({}, $.fn.scrollspy.defaults, options)
    this.$scrollElement = $element.on('scroll.scroll.data-api', process)
    this.selector = (this.options.target
      || ((href = $(element).attr('href')) && href.replace(/.*(?=#[^\s]+$)/, '')) //strip for ie7
      || '') + ' .nav li > a'
    this.$body = $('body').on('click.scroll.data-api', this.selector, process)
    this.refresh()
    this.process()
  }

  ScrollSpy.prototype = {

      constructor: ScrollSpy

    , refresh: function () {
        var self = this
          , $targets

        this.offsets = []
        this.targets = []

        $targets = this.$body
          .find(this.selector)
          .map(function () {
            var href = $(this).attr('href')
              , $href = /^#\w/.test(href) && $(href)
            return $href
              && href.length
              && [[ $href.position().top, href ]]
          })
          .sort(function (a, b) { return a[0] - b[0] })
          .each(function () {
            self.offsets.push(this[0])
            self.targets.push(this[1])
          })
      }

    , process: function () {
        var scrollTop = this.$scrollElement.scrollTop() + this.options.offset
          , scrollHeight = this.$scrollElement[0].scrollHeight || this.$body[0].scrollHeight
          , maxScroll = scrollHeight - this.$scrollElement.height()
          , offsets = this.offsets
          , targets = this.targets
          , activeTarget = this.activeTarget
          , i

        if (scrollTop >= maxScroll) {
          return activeTarget != (i = targets.last()[0])
            && this.activate ( i )
        }

        for (i = offsets.length; i--;) {
          activeTarget != targets[i]
            && scrollTop >= offsets[i]
            && (!offsets[i + 1] || scrollTop <= offsets[i + 1])
            && this.activate( targets[i] )
        }
      }

    , activate: function (target) {
        var active

        this.activeTarget = target

        this.$body
          .find(this.selector).parent('.active')
          .removeClass('active')

        active = this.$body
          .find(this.selector + '[href="' + target + '"]')
          .parent('li')
          .addClass('active')

        if ( active.parent('.dropdown-menu') )  {
          active = active.closest('li.dropdown').addClass('active')
        }

        active.trigger('activate')
      }

  }


 /* SCROLLSPY PLUGIN DEFINITION
  * =========================== */

  $.fn.scrollspy = function ( option ) {
    return this.each(function () {
      var $this = $(this)
        , data = $this.data('scrollspy')
        , options = typeof option == 'object' && option
      if (!data) $this.data('scrollspy', (data = new ScrollSpy(this, options)))
      if (typeof option == 'string') data[option]()
    })
  }

  $.fn.scrollspy.Constructor = ScrollSpy

  $.fn.scrollspy.defaults = {
    offset: 10
  }


 /* SCROLLSPY DATA-API
  * ================== */

  $(function () {
    $('[data-spy="scroll"]').each(function () {
      var $spy = $(this)
      $spy.scrollspy($spy.data())
    })
  })

}( window.jQuery );